Local interconnect network receiver

ABSTRACT

The present invention relates to a LIN receiver having sleep/wake-up functionality, which has an input (LINI) to a LIN bus (LIN), an output (RXDO), terminals for at least one supply voltage (BVDD), and transistors (M 1  through M 17 ), the transistors (M 1  through M 17 ) being switched to activate the receiver in the recessive state of the LIN bus via a state change on the LIN bus into an active state of the receiver. In particular, the input (LINI) is connected between components of a voltage-to-current converter (SSW), in particular between a first and a second resistors, (R 2 , R 2 ).

The present invention relates to a LIN receiver having a sleep/wake-up functionality according to the definition of the species in Patent Claim 1.

LIN Receivers (LIN: Local Interconnect Network) are designed to recognize a level on a LIN bus. According to LIN specification 2.1, page 115, voltage dividers having different division ratios are used on the LIN bus and on the [power] supply, in particular a battery, to evaluate a LIN level on the bus. FIG. 6 shows an exemplary configuration according to the present prior art. A voltage divider chain composed of two resistors is connected between a ground voltage GND and a terminal or input LINI to the LIN bus. Another voltage divider chain also composed of two resistors is connected between ground GND and a positive supply voltage of the BVDD bus. The terminal for ground GND may also be connected as negative supply voltage of the bus. Contact points between the two resistors of the two voltage divider chains lead to a positive and negative input, respectively, of an operational amplifier having an RXDO output, to which data, in particular received RXD data are applied as essentially known.

The disadvantage of such an approach is the permanent power consumption of the divider chains and the required chip surface area for implementing high-impedance resistors. This makes a compromise between power consumption and chip surface area necessary. To implement a sleep function, the divider chains may be switched off. This results in that the level on the LIN bus can no longer be correctly evaluated and a wake-up function over the LIN bus is no longer possible. Accordingly, currently available LIN receivers and LIN transceivers having an integrated receiver function have a relatively high power consumption in the sleep mode.

The object of the present invention is to propose a circuit configuration or a LIN receiver having a corresponding circuit configuration which allow the power consumption to be reduced in the sleep mode.

This object is achieved by a LIN receiver having a sleep/wake-up functionality and the features of Patent Claim 1. Advantageous embodiments are the subject matter of dependent claims.

Accordingly, in particular a LIN receiver having a sleep/wake-up functionality is preferably [provided], which has an input to a LIN bus, an output, and terminals for at least one supply voltage, the LIN receiver also having transistors which are switched to activate the receiver in the recessive state of the LIN bus via a state change on the LIN bus into an active state of the receiver.

The LIN receiver does not necessarily have to be understood here as an independent component. They also include appropriate circuit configurations, in particular circuit configurations in higher-level devices having such a LIN receiver functionality. This is true, in particular for LIN transceivers, which, in addition to a receiver functionality, also have a transmitter functionality.

In particular, a preferred LIN receiver of this type is characterized by very low power consumption in the recessive state of the LIN bus, i.e., in the sleep function [sic; mode]. Nevertheless, the receiver may be automatically activated via a state change on the LIN bus into the active, or dominant, state, which provides a wake-up functionality. During the wake-up, i.e., activation or thereafter, the LIN receiver may then generate a signal, using which a processor may be activated, for example, via an interrupt.

This results in a plurality of advantages. Except for leak currents, no current is consumed in the sleep mode. Depending on the specific embodiment, no high-impedance voltage dividers are needed. Even in the active mode, only a low current consumption is required [sic; occurs]. In particular, automatic activation of the circuit is enabled in the event of activity on the LIN bus, so that a specific wake-up signal is not required. The hysteresis is advantageously proportional to the supply voltage.

In particular, such a LIN receiver, in which the input is connected between components of a voltage-to-current converter, is preferably connected between a first and a second resistor in particular.

In particular, a first resistor of the voltage-to-current converter is connected and dimensioned as a pull-up resistor in such a way that, in the case of a dominant level at the input, current flows through the first resistor. At least one first, second, and third transistor is preferably connected to minor the current flow through the first resistor, and at least one eighth and one fourteenth transistor and additional twelfth, thirteenth, and fifteenth transistors connected as cascode transistors are preferably connected to switch the LIN receiver and/or the output into the active mode.

In the LIN receiver, a second resistor of the voltage-to-current converter is advantageously connected so it may be connected to a negative supply voltage or to ground with the aid of transistors.

At least one third and one fifteenth transistor may be connected between a positive supply voltage and the negative supply voltage or ground for comparing a current flow component through the first resistor and a current flow component through the second resistor.

One tenth and one eleventh transistor may be connected to the third and fifteenth transistors on the output side, in order to pull the output toward ground or to the negative supply voltage of the bus.

At least one fourth, one fifth, and one seventh transistor may be connected between the positive supply voltage and the negative supply voltage or to ground in such a way that a current flow component through the second resistor of the voltage-to-current converter activates the gate terminal of the seventh transistor and, through it, the fourth and the fifth transistors for compensating the current component through the second resistor [TN: The word “über” was omitted in the translation]. The current is mirrored onto the input by the fourth and fifth transistors. Viewed from the LIN bus outward, the second resistor thus becomes invisible.

In addition, at least one eighth and one fourteenth transistor may be connected between the positive supply voltage and the negative supply voltage or ground in such a way that, at recessive level at the input, they switch off a current flow through the second resistor with the aid of a switch. They may switch off the current flow, for example, via a twelfth transistor, which is activated using these transistors and is connected between the second resistor and the negative supply voltage or ground. The entire circuit thus becomes ultimately de-energized. This results in a low power consumption at the most, which, in the recessive state, is limited to leak currents both on the LIN bus and on the supply terminal.

A switch and, for generating a hysteresis, a seventeenth transistor may be connected as additional components in series between the second resistor and the negative supply voltage or ground, the switch then being switched to switch a current flow through the seventeenth transistor on or off, depending on a switching state at the output. Such a circuit configuration results in a hysteresis whose value is not constant, but proportional to the supply voltage. This behavior is advantageous, since the definition of hysteresis in the LIN specification refers to the supply voltage.

In general, the transistors may be dimensioned, with the aid of scaling factors, to appropriately reduce all currents, except those through a first resistor of the voltage-to-current converter, connectable to the positive supply voltage. Even high scaling factors are possible here, since the speed requirements in LIN receivers of this type are low if the maximum frequency of the LIN bus is fmax(LIN)=20 kHz in particular.

A sixteenth transistor may be connected as an integrated polarity reversal protection diode between a positive supply voltage and the other transistors. Due to an appropriate wiring of the gate of the sixteenth transistor, it is in Rdson mode in the case of a bus supply voltage of normal polarity, due to which, if it is appropriately dimensioned, a voltage drop may be neglected.

Since the above-named transistors are labeled with numbers, this is only a labeling feature for differentiating the individual transistors and not a numbering in the meaning of a numerical listing.

According to aspects deserving special mention, disadvantages are thus eliminated, depending on the design of the specific embodiments, by eliminating the divider chains on the supply or supply voltage by using the pull-up resistor prescribed by the LIN specification for signal evaluation. In addition, the entire circuit may be deactivated in the recessive state on the LIN bus. In the non-recessive state on the LIN bus, automatic activation may take place.

An exemplary embodiment is described below with reference to different specific embodiments. Identical reference numerals in the different figures refer to identical or identically working components and functions, so that, in particular in the case of extended specific embodiments, reference is also made to the embodiments of the other and, in particular, previous figures regarding such identical reference numerals. In general, components of the other specific embodiments may, of course, be combined directly with the first specific embodiment even without specific embodiments described as connected in between.

FIG. 1 describes a circuit configuration of a first preferred LIN receiver;

FIG. 2 shows a second circuit configuration of a LIN receiver modified with respect thereto;

FIG. 3 shows a specific embodiment of a LIN receiver further modified with respect to FIG. 2;

FIG. 4 shows a specific, still further modified, embodiment of a LIN receiver of this type;

FIG. 5 shows another specific embodiment of a LIN receiver of this type, modified with respect to FIG. 1;

FIG. 6 shows an exemplary configuration according to the prior art.

FIG. 1 shows an exemplary circuit configuration having an input LINI as connecting point for a LIN bus LIN, an RXDO output, at which received RXD data may be picked off, a positive supply voltage of the BVDD bus, and a negative supply voltage of the BVSS bus. As essentially known, the relative ratio of the negative and positive supply voltages BVSS, BVDD of the bus is relevant. In particular, the negative supply voltage may optionally also correspond to the ground terminal [voltage]. In addition, a supply voltage VDD is applied to the circuit configuration.

Input LINI is connected between a first and a second ohmic resistor R1, R2. First resistor R1 may have an impedance of 35 k [sic; kΩ?], for example. The first and second resistors R1, R2, thus form a voltage-to-current converter SSW.

The terminal of first resistor R1 facing away from input LINI is connected to a first transistor M1, specifically to [its] drain and gate. The source and bulk of first transistor M1 are also connected to the positive supply voltage of the BVDD bus. In addition, the second terminal of first resistor R1 facing away from input LINI is connected to a second transistor M2 and a third transistor M3, specifically to their gates. The source and bulk terminals of second and third transistors M2, M3 are connected to the positive supply voltage of the BVDD bus.

In addition, the positive supply voltage of the BVDD bus is applied to a fourth and a fifth transistor M4, M5, specifically to their source and bulk terminals. In addition, input LINI is connected to the drain of fourth transistor M4. The gate terminals of fourth and fifth transistors M4, M5 are connected to the drain of fifth transistor M5.

The second terminal, facing away from input LINI, of second resistor R2 is connected to the negative supply voltage of the BVSS bus via a twelfth and a sixth transistor M12, M6. Second resistor R2 is connected to the source of twelfth transistor M12, the drain of twelfth transistor M12 is connected to the source and gate of sixth transistor M6, and the drain of sixth transistor M6 is connected to the negative supply voltage of the BVSS bus.

The gate terminal of twelfth transistor M12 is connected to a node shared with gate terminals of a thirteenth transistor M13, of a fourteenth transistor M14, and of a fifteenth transistor M15. In addition, this node is connected to the source of fourteenth transistor M14 and to the drain of second transistor M2. In addition, the source of thirteenth transistor M13 is connected to the gate terminal of fourth and fifth transistors [M4,] M5. In addition, the source of fifteenth transistor M15 is connected to the drain of third transistor M3.

The gate terminal of sixth transistor M6 is jointly connected to the gate terminals of a seventh transistor M7 and a ninth transistor M9. The drain of thirteenth transistor M13 is connected to the source of seventh transistor M7, and the drain of seventh transistor M7 is connected to the negative supply voltage of the BVSS bus. The drain of fourteenth transistor M14 is connected to the source and gate of an eighth transistor M8. The drain of eighth transistor M8 is connected to the negative supply voltage of the BVSS bus. The source of ninth transistor M9 is connected to the drain of fifteenth transistor M15, and its drain is connected to the negative supply voltage of the BVSS bus.

The gate terminals of a tenth and an eleventh transistor M10, M11 are connected to both the source of tenth transistor M10 and the drain of third transistor M3. The drain terminals of tenth and eleventh transistors M10, M11 are connected to the negative supply voltage of the BVSS bus. The drain of eleventh transistor M11 is connected both to a current source whose other input corresponds to supply voltage VDD and to a Schmitt trigger whose output terminal corresponds to the RXDO output.

The first five transistors M1 through M5 are preferably designed as MOSFETs. In principle, however, the use of bipolar transistors, instead of MOSFETs, is also possible.

Regarding its functionality, first resistor R1 corresponds to the pull-up resistor prescribed in the LIN specification. At the dominant level (low) on the LIN bus, i.e., on the LINI input, current flows through first resistor R1. This current flow is mirrored via the configuration of first, second, and third transistors M1 through M3 and activated via eighth and fourteenth transistors M8, M14 and via twelfth, thirteenth, and fifteenth transistors M12, M13, M15 connected as cascode transistors. A current, which is mirrored by sixth, seventh, and ninth transistors M6, M7, M9, thus also flows through second resistor R2.

At the connection of third and fifteenth transistors M3, M15 the two current components are compared via the two resistors R1, R2. If the component through first resistor R1 dominates, a current flow occurs in tenth transistor M10, which is mirrored via eleventh transistor M11 and thereby pulls the RXDO output toward ground or the negative supply voltage of the BVSS bus.

The current component through second resistor R2 is undesirable in principle, since it is not provided in the LIN specification. Therefore, the current component is preferably compensated by second resistor R2. For this purpose, the current from seventh transistor M7 is mirrored onto input LINI via fifth and fourth transistors M5, M4. Viewed from the LIN bus outward, second resistor R2 thus becomes invisible.

At a regressive level on the LIN bus (high), there is no current flow in first resistor R1, whereby eighth and fourteenth transistors M8, M14, which are wired as MOS diodes, are switched off. The current flow in second resistor R2 is thus suppressed by twelfth transistor M12, and the entire circuit becomes de-energized. This results in no high power consumption, which is limited to leak currents both on the LIN bus and on the supply terminal.

FIG. 2 shows a modified specific embodiment, which is used for reducing the power consumption in the active mode. Scaling factors n and/or m may be introduced for this purpose. For example, if a second scaling factor m is provided on the first, fourth, and sixth transistors M1, M4, M6, a factor 1 is provided on second, third, fifth, and seventh transistors M2, M3, M5, M7, and a first scaling factor n is provided on ninth transistor M9. Second resistor R2 is dimensioned as the product of first scaling factor n and resistance 35 k[Ω], for example, of first resistor R1. This reduces all currents except those through first resistor R1 accordingly. Since the speed requirements for LIN receivers of this type are low because the maximum frequency of the LIN bus is fmax(LIN)=20 kHz, high scaling factors may be selected accordingly.

FIG. 3 shows a specific embodiment which is extended with respect to the specific embodiment according to FIG. 2 by a sixteenth transistor M16, which is preferably another MOSFET. As is true also for the other transistors, however, appropriate circuits having bipolar transistors instead of field-effect transistors may also be constructed. Sixteenth transistor M16 is used as an integrated polarity reversal protection diode, the gate of sixteenth transistor M16 being connected to the gate of first transistor M1. [Its d]rain and source are connected between the positive supply voltage of the BVDD bus and the source terminals of first through fifth transistors M1 through M5. The positive supply voltage of the BVDD bus is thus no longer directly connected to the latter. Due to the wiring of the gate of sixteenth transistor M16, in the case of normal polarity of the supply voltage of the BVDD bus, it is in the Rdson mode (Rdson=closing resistor or drain-source resistor), due to which, in the case of appropriate dimensioning, the voltage drop may be neglected.

FIG. 4 shows a further modified specific embodiment, which has additional components compared to the specific embodiment depicted in FIG. 3.

The circuit configuration according to FIG. 4 also implements a hysteresis by using a seventeenth transistor M17, which is designed as a bipolar transistor, for example. In addition, the configuration has a switch S, which may be designed, for example, as an NMOS transistor. Specifically, the gate of seventeenth transistor M17 is connected, among other things, to the gate of sixth transistor M6 and will activate sixth transistor M6. The source of seventeenth transistor M17 is connected to the negative supply voltage of the BVSS bus. The drain of seventeenth transistor M17 is connected to one terminal of switch S. The other terminal of switch S is connected to the source terminal of twelfth transistor M12. Switch S is connected through a connection to a node, which connects the drain terminal of eleventh transistor M11 to the Schmitt trigger and the voltage source. Such a circuit configuration results in a hysteresis whose value is not constant, but proportional to the supply voltage. This behavior is advantageous, since the definition of hysteresis in the LIN specification refers to supply voltage BVDD.

In addition to the different depicted specific embodiments, a plurality of further implementation options exist for achieving a reduced or entirely non-existent power consumption. For example, bipolar transistors may be used instead of MOSFETs. In particular, an appropriately designed circuit configuration may also be implemented, which uses another voltage-to-current converter SSW instead of the one depicted composed of first and second ohmic resistors R1, R2. Thus, for example, MOS transistors connected as resistors may be used instead of first and second resistors R1, R2.

In addition, additional cascodes, in particular NMOS and/or PMOS, may be used for enhancing the accuracy and/or voltage resistance in a corresponding circuit configuration. The use of additional protection elements which do not affect the mode of operation in principle, in particular resistors and/or Zener diodes, is also possible for enhancing the sturdiness of such a circuit configuration.

In particular, a current signal, instead of a voltage signal may be extracted by appropriately reconfiguring the circuit configurations.

Additionally switching over seventh transistor M7 is also advantageous for adapting the compensation current to the hysteresis switchover, since in the depicted circuit configuration the compensation via the influence of the hysteresis transistor is not yet altogether ideal. 

1. A LIN receiver having sleep/wake-up functionality, comprising: an input (LINI) to a LIN bus (LIN), an output (RXDO), and a terminals for at least one supply voltage (BVDD), wherein a plurality of transistors which are connected for activating the receiver in recessive state of the LIN bus via a state change on the LIN bus into an active state of the receiver.
 2. The LIN receiver of claim 1 wherein the input (LINI) is connected between components of a voltage-to-current converter (SSW), in particular between a first resistor and a second resistor (R1, R2).
 3. The LIN receiver of claim 2, wherein a first resistor (R1) of the voltage-to-current converter (SSW) is connected and dimensioned as a pull-up resistor in such a way that, in the case of dominant level at the input (LINI), current flows through the first resistor (R1).
 4. The LIN receiver of claim 3, wherein the plurality of transistors includes at least first, second, and third transistors (M1 through M3), which are preferably connected to mirror the current flow through the first resistor (R1), and at least one eighth and one fourteenth transistor (M8, M14) and additional twelfth, thirteenth, and fifteenth transistors (M12, M13, M15) connected as cascode transistors which are connected to switch the LIN receiver and/or the output (RXDO) into the active mode.
 5. The LIN receiver of claim 4, wherein a second resistor (R2) of the voltage-to-current converter (SSW) is wired so it may be connected to a negative supply voltage (BVSS) or to ground with the aid of the twelfth and sixth transistors (M12, M6).
 6. The LIN receiver of claim 5, wherein at least one third and one fifteenth transistor (M3, M15) are connected between a positive supply voltage (BVDD) and the negative supply voltage (BVSS) or ground for comparing a current flow component through the first resistor (R1) and a current flow component through the second resistor (R2).
 7. The LIN receiver of claim 6, wherein a tenth and an eleventh transistor (M10, M11) are connected to the third and fifteenth transistors (M3, M15) on the output side, in order to pull the output (RXDO) toward ground or toward the negative supply voltage (BVSS) of the bus.
 8. The LIN receiver of claim 5, wherein at least one fourth, one fifth, and one seventh transistor (M4, M5, M7) are connected between a positive supply voltage (BVDD) and the negative supply voltage (BVSS) or ground in such a way that a current flow component through the second resistor (R2) of the voltage-to-current converter (SSW) activates the gate terminal of the seventh transistor (M7) and, through it, the fourth and the fifth transistors (M4, M5) for compensating the current component through the second resistor (R2).
 9. The LIN receiver of claim 8, wherein at least one eighth and one fourteenth transistor (M8, M14) are connected between a positive supply voltage (BVDD) and the negative supply voltage (BVSS) or ground in such a way that, at recessive level at the input (LINI), they switch off a current flow through the second resistor (R2) with the aid of a switch.
 10. The LIN receiver of claim 9, wherein a switch (S) and, for generating a hysteresis, a seventeenth transistor (M17) are connected as additional components in series between the second resistor (R2) and the negative supply voltage (BVSS) or ground, the switch (S) then being switched to switch a current flow through the seventeenth transistor (M17) on or off, depending on a switching state at the output (RXDO).
 11. The LIN receiver of claim 1, wherein the transistors are dimensioned, with the aid of scaling factors (m, n, 1), to appropriately reduce all currents, except those through a first resistor (R1) of the voltage-to-current converter (SSW).
 12. The LIN receiver of claim 10, wherein a sixteenth transistor (M16) is connected between a positive supply voltage (BVDD) and the other transistors as an integrated polarity reversal protection diode. 